[Db.OeBoundFunction(CollectionFunctionName = "BoundFunctionCollection", SingleFunctionName = "BoundFunctionSingle")]
public static IEnumerable<Order> BoundFunction(Db.OeBoundFunctionParameter<Customer, Order> boundParameter, IEnumerable<String> orderNames)
{
    //create DbContext
    OrderContext orderContext = boundParameter.CreateDataContext<OrderContext>();
    //apply query part before bound function - Customers/$filter(Sex eq 'Female')
    IQueryable<Customer> customers = boundParameter.ApplyFilter(orderContext.Customers, orderContext);
    IQueryable<Order> orders = customers.SelectMany(c => c.Orders).Where(o => orderNames.Contains(o.Name));
    //apply query part after bound function - $expand=Customer,Items&$select=Name
    IQueryable result = boundParameter.ApplySelect(orders, orderContext);
    List<Order> orderList = boundParameter.Materialize(result).ToListAsync().GetAwaiter().GetResult();
    boundParameter.CloseDataContext(orderContext);
    return orderList;
}